Issue No. 20 July 2009 21 Abstract: Dyes and dyeing processes are very important subjects for textile conservators. The textile conservation ield has been traditionally divided into those who use synthetic dyes and those who use natural dyes. This study aims to give the outline of this conlict and giving recommendations for textile conservators on which type of dyes can be used safely in textile conservation. In this study silk textile samples were dyed with selected natural and synthetic dyes. The dyed silk textile samples were artiicially aged by light for various periods. The changes in the colour of dyed silk textile samples after ageing by light were observed visually and using an Optimacth 3100 colour Spectrophotometer. This study conirms that both natural and synthetic dyes are important in textile conservation ield. This study concludes that if it is possible to achieve the required colour shade using natural dyes, it is recommended to use natural dyes. But if it is not possible to achieve the required colour shade using natural dyes, then synthetic dyes are recommended. 1. Introduction Dyes are coloured compounds which can bond to ibres and colour them (Tímár-Balázsy and Eastop, 1998). Dyes and dyeing processes are very important tasks for textile conservation purposes. Dyes are commonly used for dyeing fabrics that can be used in various processes of textile conservation (Abdel-Kareem, 2002, Kajitani, 1987). These dyed fabrics can be used in lining and supporting weakened textile, rugs, tapestries and carpets (Kajitani, 1987, Marko, 1987, Zidan, 1987, Flury-Lemberg, 1988, Ennes, 1991, Hutchison, 1991, Landi, 1998, Abdel-Kareem, 2004). Dyed fabrics can be used in compensation and for completing lost areas in tapestries and carpets (Green and Swetzoff, 1991, Mailand, 1991, Merritt, 1991, Perkins, et al, 1991). The aesthetic conservation processes of textiles depend on the success in selecting the suitable colour for the lining fabric, to give a desirable appearance during the display of the textile object (Flury-Lemberg, 1988). Also dyes are used for dyeing the threads used for ixing any damage in textile objects or ixing the object with lining fabrics (Flury-Lemberg, 1988, Landi, 1998, Nola, et al, 2002, Abdel-Kareem, 2002). Dyed threads can be used in compensation and completion of any lost areas in tapestry textiles and carpets (Green and Swetzoff, 1991, Mailand, 1991, Merritt, 1991, Perkins, et al, 1991, Abdel-Kareem, 2004). Dyes are used in the preparation of textile samples simulating an ancient one to be used as experimental samples and can be used in the evaluation of any new materials or methods suggested to be used in the conservation of textile objects (Abdel-Kareem and Morsy, 2004, Abdel-Kareem, 2006, Abdel- Kareem, and Al-Saad, 2007). For preparing dyed textile samples to simulate historical ones it is not dificult to decide which dyes can be used because the selected dyes should be the same as the dye used on the original objects, which has been determined by analysis. But it is too dificult to decide which type of dyes should be used for dyeing the materials that will be used for conservation purposes (Abdel-Kareem, 2002). The success of conservation of a textile object ISSN: 1319-8947 (pp.21-36) Omar Abdel-Kreem Evaluation of the Dyes used in Conservation and Restoration of Archaeological Textiles